Immersion heaters are commonly used in a variety of food equipment such as steam tables. Generally these heaters are electrical heating devices placed at the bottom of a water tank and are used for heating water to produce steam, which is primarily used for heating food. These heaters generally consist of one or more copper tubes bent in various coil configurations, each containing an insulated electrical coil which transmits heat through the copper tubing to the water.
Heaters are typically protected against overheat hazards by a thermally activated mechanical switch placed elsewhere in the heater assembly. The mechanical switch commonly used consists of a heat sensitive actuator rod which expands sufficiently in an overheat condition to actuate a microswitch which controls power to the heaters.
Over a period of time, however, problems occur when the copper tubes of the heater and actuator rod corrode. When the heater corrodes, lime deposits form along the exterior surfaces of the tubes. These deposits eventually build up and bridge the gaps between the windings of each of the tubes, creating hot spots which cause heater failure. It is often a difficult task to remove these lime deposits to avoid heater failure because of the size and location of these devices.
The thermally activated actuator rod corrodes independently. Corrosion causes the actuator rod to deteriorate so that it fails to operate properly; sometimes it fails to operate at all. Under these conditions damage can occur to the equipment and environs and/or the heater may destroy itself.